Double exhaust valve for gas blast circuit-breakers including a check valve and underpressure responsive valve

ABSTRACT

Metal clad gas blast circuit breaker which is exclusively adapted to interrupt a circuit, the switching element thereof being accommodated in a metal casing containing high-pressure and low-pressure compartments filled with insulating gas under overpressure, said circuit breaker comprising a safety valve and means to control said valve in such a manner, that the overpressures in said compartment can never fall below predetermined values.

United States Patent DOUBLE EXHAUST VALVE FOR GAS BLAST CIRCUIT-BREAKERS INCLUDING A CHECK VALVE AND UNDERPRESSURE RESPONSIVE VALVE 2 Claims, 1 Drawing Fig.

US. Cl .Q 200/148 Int. Cl ..l-l01h33/54,- HOlh 33/80, HOlh 33/86 Field of Search 200/ 148, 148.2, 148.5

[56] References Cited UNITED STATES PATENTS 3,141,942 7/1964 Forwald ZOO/148 3,214,540 10/1965 Schromeck et al. 200/148(.2)X 3,250,970 5/1966 Passaquin 200/148(.5) 3,268,697 8/1966 Morioka 200/148 Primary ExaminerDavid Smith, Jr. Assistant Examiner- Robert A. Vanderhye Attorney-Snyder & Butrum PATENTED F581 6 I9?! INVENTORS 'Ri NTJE 80E RSNA m'JsaERT w. IRiK BY /9 ATTORNIiYJ DOUBLE-EXHAUST VALVE FOR GAS BLAST CIRCUIT- BREAKERS INCLUDING A CHECK VALVE AND UNDERPRESSURE RESPONSIVE VALVE The invention relates to a metal clad gas blast circuit breaker exclusively adapted to interrupt a circuit and comprising a metal casing and a switching element accommodated in and insulated from said casing, said switching element being surrounded by a high-pressure-compartment filled with gas under overpressure and said switching element comprising at least two switching contacts adapted to be separated from one another to interrupt the circuit, at least one of said contacts being formed as a tubular contact, the passage of which is closed by the other switching contact, the passage of which is closed by the other switching contact in the closed position of the circuit breaker and opens into a low-pressure-compartment filled with gas under lower overpressure, so that the high-pressure-compartment and the low-pressure-compartment are separated from one another in the closed position of the circuit breaker but are in open communication with one another through said tubular contact during the switching-off process, said low-pressure-compartment being connected to a discharge conduit provided with a spring loaded check valve which keeps said discharge conduit closed, when the pressure ofthe gas contained in the low-pressure-compartment has a value which is lower than a marginal value corresponding to a predetermined overpressure, and opens said conduit when said pressure-exceeds said marginal value.

ln gas blast circuit breakers of this kind there exists the danger that, if the check valve provided in the discharge conduit should stick in its open position or leak so heavily that the gas supply device will not be able to maintain the overpressure required in the low-pressure-compartment, the pressure of the gas contained in the low-pressure-compartment will fall to almost the pressure of the atmosphere or to an overpressure which is too low and, if the switching contacts should'remain separated after the switching-off process or leak so heavily in the closed position of the circuit breaker that the gas supply device will not be able to maintain the overpressure required in the high-pressure-compartment, the pressure of the gas contained in the high-pressure-compartment will fall to almost the overpressure-required in the low-pressure-c'ompartment or to a higher overpressure which is still too low. Since the gas contained in the compartments of the circuit breaker is required to insulate the live parts thereof, a fall of the pressures in said compartments below the lowest overpressures allowed will endanger the meant insulation. i The invention has the object to avoid entirely or substan tially said danger. It consists in that the discharge conduit comprises a second valve acting as a safety valve and means to control said safety valve are provided, said means keeping the safety valve in its open position, when the pressure in the highpressure-compartment and the pressure in the low-pressurecompartment have values which are higher than marginal values which exceed the lowest pressures allowed in said compartments by predetermined values, and close the safety valve,

when the pressure in the high-pressure-compartment and (or) the pressure in the low-pressure-compartment fall(s) below said marginal value Y A simple construction to achieve the object aimed at is obtained when the means to control the safety valve consists of a spring adapted to close said safety valve and in a double acting cylinder containing a piston adapted both to open and to close said safety valve, the space of said cylinder for pushing the safety valve open being in open communication with the lowpressure-compartment and the space of said cylinder for closing the safety valve being adapted to be connected by a changeover valve either with the atmosphere or with the high-pressure-compartment, said changeover valve being controlled by a spring and a single acting cylinder containing a piston which counteracts said spring,-said spring trying to force the changeover'valve into the position, in which the relevant cylinder space of the double acting cylinder is connected with the highpressure-compartment, and the active cylinder space of the drawing, which illustrates a vertical sectional view of a gas blast circuit breaker constructed inaccordance with the in vention.

In the drawing the gas blast circuit breaker, which is exclusively adapted to interrupt the circuit, is provided with a metal casing 1, in which the switching element is accommodated and supported by insulators 2 and 3, so that it is insulated from said casing. This switching element consists of two fixed tubular contacts 4, 5 and an axially movable annular switching contact 6 cooperating therewith. This switching contact is connected by an insulating rod 7 with a driving rod 8. The fixed tubular contacts 4, 5 are each carried by and open each into a metal expansion chamber 9, 10 provided with cooling rings ll, 12. These expansion chambers 9, 10 are each connected with a conductor 15, 16 led through a bushing insulator 13, 14 for the connection of the circuit breaker with the outer circuit.

' In its state of rest the circuit breaker is closed and the compartment 17 surrounding the switching element 4, 5, 6 and the expansion chambers 9, 10 is separatedin a gastight manner from the compartments 18, 19, 20, which are found within the expansion chambers 9, 10 and above the expansion chamber 10 and communicate with one another through conduits 21 of insulating material. The compartment 17 is filled with insulating gas under the high pressure p,, which, in the state of rest, that means when the circuit breaker is closed, is for instance 15 atm. In the state of rest of the circuit breaker the compartments 18, 19, 20 are filled with the same insulating gas under the lower pressure b which for instance is 5 atm. Consequently, all compartments within the casing 1 contain insulating gas under overpressure. Owing to the use of gas under overpressure the insulating value of the gas filling is increased considerably and the insulating distances in the circuit breaker can be made smaller than in the case where only gas under atmospheric pressure is used. However, this means, that should the overpressures of the insulating 'gas become too low the insulation of the life parts of the circuit breaker will become insufiicient and danger for an earth leakage current will arise.

- The gas is supplied through a conduit 22 to the high-pressurecompartment. 17 and through a conduit 23 to the low-pressure-compartment 18, 19, 20.

During the switching-off process the movable switching contact 6 is moved upwards, so that it is separated from the fixed tubular contact 4 and the high-pressure-compartment 17 is brought into open communication with the low-pressurecompartment 18, 19,20. Strong currents of gas to extinguish the switching arc then flow from the high-pressure-compartment through the tubular contacts '4, 5 to the compartments 18, 19 in the expansion chambers 9, 10 and hence through "tubes 21 to the compartment 20, so that the pressure in the high-pressure-compartment decreases and the pressure in the low-pressure-compartment 18, 19, 20 increases. The lowpressure-compartment 20 is connected to a discharge conduit 24, which, in the state of rest of the circuit breaker, is closed by a check valve 26 loaded by a spring 25. The spring 25 is so adjusted by means of the adjusting screw 27 as to maintain in 4 the low-pressure-compartment 18,19, 20 a pressurep If, for instance during the switching off process, the pressure in the low-pressure-compartment 18, 19, 20 should rise, the check valve 26 will be pushed open, so that the excess of gas will escape to the atmosphere through a sound absorber 28. After 3 and could fall below the lowest pressure p allowed, which is lower than the operational pressure p say 3,5 atm. It could also happen that the movable switching contact 6 sticks in theopen position after the switching-off process or leaks so heavily in the closed position of the circuit breaker, that the supply device is not able to supply the loss of gas caused thereby from I the high-pressure-compartment 17. in that case the pressure in the high-pressure-compartment 17 could fall below the lowest pressure p" allowed in said compartment, said lowest pressure being lower than the operational pressure p,, say atm. In both cases the insulation in the circuit breaker would beendangered.

In order to avoid this danger there is provided according to cylinder 32. The space 33 of this cylinder is in open communication with the low-pressure-compartment 18, 19, 20 and the space 34 of this cylinder is connected through aconduit 35 with-the chamber 36 of a changeover-valve 37, which in the shown end position connects thecylinder space 34 through the conduit 35, the chamber 36and an opening 38 with the atmosphere and in the other end positioncloses the opening 38 and connects said cylinder space 34 through the conduit 35, the chamber 36 and an opening 39 with the active cylinder space 40 of 'a single acting cylinder 41 which is provided with a piston 44 loaded by a spring 43 which can be adjusted by means of an adjusting screw 42. The cylinder space 40 is connected with the high-pressure-compartment by a conduit 45.

The spring 30 andthe piston 31 are dimensioned, in such a manner, that,- if the gas pressure in the low-pressure-compartment l8, 19, 20. be higher than p "+AP the force exerted on the piston 31 is greater than the force of the spring 30. How ever, if said gas pressure should fall below the value p '+Ap the force of the spring 30 will exceed the force exerted on the piston 31, so that the safety valve 29 will be pushed upwards and the discharge conduit 24 will be closed.

The spring 43 is so adjusted and'the piston 44 is so dimensio'ned, that, if the gas pressure in the high-pressure-compartment be higher than p,'+Ap,, the force exerted on the piston 44 will be greater than the force of the spring 43, so that the changeover valve 37 is positioned in the shown position, that means that said valve 37 then opens the opening 38 towards the atmosphere and closes the opening 39 towards the cylinder space 40 and the high pressu re-compartment 17. However, should the pressure in the high-pressure-compartment fall below the value p,'+Ap,, the force of the spring 43' will become greater than the force exerted on the piston 44, so that the changeover valve 37 will be changed over, the opening 38 will be closed and the opening.39 will be opened. This has the result that the cylinder space 34 beneath the piston 31 i the inventiona safety valve 29 which sees to it that the discharge conduit 24 is closed when the pressures in the highis connected with the high-pre'ssure-compartment 17 and the 7 safety valve 29 is moved upwards to close the discharge conduit 24. Consequently, the gas pressures in the high-pressure.

compartment and the low-pressure-compartment can never become lower than p1 +Ap, and p,'+Ap,, respectively.

If the safety valve 29 has come into action an auxiliary switch 46 is closed which act uates a-signaling device (not shown).

From the above it is learned that the gas blast circuit breaker must be so constructed and must operate in such a manner, that the quantity of gas required to extinguish the switching arc will not decrease the pressure in the high-pressure-compartment 17 below the value p,'+Ap, atm. in some cases the closing of the safetyvalve can also be used to reduce the quantity of extinguishing gas used during the switching-off process. Furthermore, the gassuplply device must be so adusted that the supply of gas to the ow-pressure-compartment only takes place when the pressure in said compartment has fallen to a value below p '+Ap- We claim:

1. A metal clad gas blast circuit breaker exclusively adapted to interrupt a circuit and comprising a metal casing and a switching element accommodated in and insulated from said casing, said switching element being surrounded by a highpressure-compartment filled with gas under overpressure and said switching element comprising at least two switching contacts adapted to be separated-from one another to interrupt the circuit, at least one of said contacts being formed as a tubular contact, the passage of which is closed by the other switching contact in the closed position of the circuit breaker and opens into a low-pressure-compartrnent filled with gas under lower overpressure, so that the high-pressure-compartment and the low-pressure-compartrnent are separated from one another in the closed position of the circuit breaker but are in open communication with one another through said tubular contact during the switching-off process, said low-pressure-compartment being connected to a discharge conduit provided with a spring loaded check valve which keeps said discharge conduit closed, when the pressure of the gas contained in the low-pressure-compart'ment has a value which is lower than a marginal value corresponding to a predetermined overpressure, and opens said conduit, when said pressure exceeds said marginal value, characterized in that the discharge conduit (24) comprises a second valve acting as a safety valve (29) and means (30-45) to control said safety valve (29)are provided, said means keeping the safety valve in its open position, when the pressure in the high-pressure-compartment (17) and the pressure in the low-pressure-compartment (18,19,20) have values which are higher than marginal values which exceed the lowest pressures allowed in said compartment by predetermined values and close the safety valve (29), when the pressure in the high-pressure-compartment (17) and/or the pressure in the low-pressure-compartment (18,19,20) falls below said marginal values.

2. A metal clad gas blast circuit breaker as claimed in claim 1, characterized in that the means to control the safety valve (29) consist in a spring (30) adapted to close said safety valve and in a double acting cylinder (32) containing a piston (31) adapted both to open and to close saidsafety valve, the space (33) of said cylinder (32) for pushing the safety valve (29) open being in open communication with the low-pressurecompartment (18,19,20) and the space (34) of said cylinder (32) for closing the safety valve being adapted to be connected by a changeover valve (37) either with the atmosphere or with the high-pressure-compartment (17), said changeover valve (37) being controlled by a spring (43) and a single acting cylinder (41) containing a piston (.44) which counteracts said spring (43), said spring (43) trying to force the changeover valve (37) into the position; in which the relevant cylinder space (34) of the double acting cylinder (32 is connected with the high-pressure-compartment (17), and the ac- 

1. A metal clad gas blast circuit breaker exclusively adapted to interrupt a circuit and comprising a metal casing and a switching element accommodated in and insulated from said casing, said switching element being surrounded by a high-pressure-compartment filled with gas under overpressure and said switching element comprising at least two switching contacts adapted to be separated from one another to interrupt the circuit, at least one of said contacts being formed as a tubular contact, the passage of which is closed by the other switching contact in the closed position of the circuit breaker and opens into a low-pressurecompartment filled with gas under lower overpressure, so that the high-pressure-compartment and the low-pressure-compartment are separated from one another in the closed position of the circuit breaker but are in open communication with one another through said tubular contact during the switching-off process, said lowpressure-compartment being connected to a discharge conduit provided with a spring loaded check valve which keeps said discharge conduit closed, when the pressure of the gas contained in the low-pressure-compartment has a value which is lower than a marginal value corresponding to a predetermined overpressure, and opens said conduit, when said pressure exceeds said marginal value, characterized in that the discharge conduit (24) comprises a second valve acting as a safety valve (29) and means (30-45) to control said safety valve (29) are provided, said means keeping the safety valve in its open position, when the pressure iN the high-pressure-compartment (17) and the pressure in the lowpressure-compartment (18,19,20) have values which are higher than marginal values which exceed the lowest pressures allowed in said compartment by predetermined values and close the safety valve (29), when the pressure in the high-pressure-compartment (17) and/or the pressure in the low-pressure-compartment (18,19,20) falls below said marginal values.
 2. A metal clad gas blast circuit breaker as claimed in claim 1, characterized in that the means to control the safety valve (29) consist in a spring (30) adapted to close said safety valve and in a double acting cylinder (32) containing a piston (31) adapted both to open and to close said safety valve, the space (33) of said cylinder (32) for pushing the safety valve (29) open being in open communication with the low-pressure-compartment (18,19, 20) and the space (34) of said cylinder (32) for closing the safety valve being adapted to be connected by a changeover valve (37) either with the atmosphere or with the high-pressure-compartment (17), said changeover valve (37) being controlled by a spring (43) and a single acting cylinder (41) containing a piston (44) which counteracts said spring (43), said spring (43) trying to force the changeover valve (37) into the position, in which the relevant cylinder space (34) of the double acting cylinder (32) is connected with the high-pressure-compartment (17), and the active cylinder space (40) of the single acting cylinder (41) being in open communication with the high-pressure-compartment (17). 